You for sure do not want to use high or even medium heat to dry MF towels. Any MF manufacturer that makes quality towels or any high end detail depot will tell you that you should either air dry the MF towels or use the lowest heat setting possible. Heat will eventually destroy the microfibers and cause an early demise to the effectiveness of the towel. It will make it rough to the touch and cause it to just generally suck at what it's made for.

I'm not trying to crap on the thread, and I know it's old anyway, but I think it needs to be mentioned.

Also, adding a couple of ounces of white vinegar to the rinse cycle really helps out. Do this on the normal rinse cycle and then let them go through the "extra rinse" cycle as is.

As mentioned, you want to use a detergent like All Clear or Tide clear only. You do not want any dyes, fragrances, or especially fabric softener on your MF towels.